BAP51-03,115 - 50V RF PIN Diode SOD-323 AEC-Q101 | NXP
MPN: BAP51-03,115 β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.45 | $0.45 |
| 10 | $0.36 | $3.60 |
| 100 | $0.27 | $27.00 |
| 500 | $0.21 | $105.00 |
| 1,000 | $0.17 | $170.00 |
BAP51-03,115 Overview
A PIN diode is a semiconductor device with a wide, lightly doped intrinsic layer sandwiched between P-type and N-type regions. At RF and microwave frequencies, this intrinsic layer gives the diode a controllable resistance that varies almost linearly with forward current, while presenting a very small, nearly constant capacitance under reverse bias. This unique behavior makes PIN diodes the preferred switching and signal-control element in the RF component hierarchy, positioned alongside RF amplifiers and RF switches inside the broader radio-frequency front-end category.
Key features of the BAP51-03 include low diode capacitance (0.55 pF maximum), low diode forward resistance (5.5 ohm typical series resistance at the specified forward current), and a wide operating temperature range of -65C to +150C. The combination of low capacitance and low forward resistance minimizes insertion loss when the diode conducts and reduces off-state leakage in RF signal paths, which is why it is specified for general RF applications.
Technically, the silicon PIN structure provides charge storage in the intrinsic region so that the RF signal sees an averaged resistance rather than a rectifying junction. As forward bias current increases, series resistance drops toward its 5.5 ohm minimum, enabling smooth, electronically controlled attenuation. Under reverse bias, the 50 V rating and sub-picofarad capacitance keep isolation high even at high frequencies.
Typical applications include RF attenuators, RF switches, antenna switching and AGC (automatic gain control) circuits in wireless receivers, as well as general RF signal conditioning in industrial and automotive radio systems where AEC-Q101 qualification is required.
Design consideration: set the forward bias current through an appropriate series resistor and RF choke; attenuation linearity and distortion depend directly on maintaining adequate stored charge at the highest operating frequency.
This page synthesizes distributor pricing context, drop-in alternatives, and practical design notes not found in the manufacturer datasheet. Note: per NXP product information the BAP51-03 is at end of life, so alternatives should be evaluated early in any new design. Pricing shown reflects typical distributor levels as of 2026-09-14.
Drop-in alternatives for BAP51-03,115 β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with BAP51-03,115 (same form factor and footprint) β differing in Forward Current (IF), Package, Reverse Voltage (VR).
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
BAP51-02,115
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
BAP64-02,115
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
BAP64-03,115
β Drop-In β οΈ εζ°εΎ ιͺθ―β In Stock
$0.09 / Unit
View Datasheet βBAP51-03,115 Maximum Ratings & Electrical Characteristics
| Diode Type | RF PIN diode, single |
| Application Category | General RF applications |
| Reverse Voltage (VR) | 50 V |
| Forward Current (IF) | 50 mA |
| Power Dissipation (Ptot) | 500 mW |
| Diode Capacitance (Cd) max @ VR, f | 0.55 pF |
| Forward Resistance (Rs) @ IF | 5.5 ohm |
| Operating Temperature Range | -65 C to +150 C |
| Automotive Qualification | AEC-Q101 qualified |
| Package | SOD-323 (SC-76), 2-pin |
| Package Body Dimensions | 1.7 mm x 1.25 mm x 0.95 mm |
| Lead Pitch | 1.3 mm |
| Terminal Form | Gull wing |
| Mounting Type | Surface Mount |
| Shipping Packaging | Tape and Reel |
BAP51-03,115 Pin Configuration
| Pin 1 | Anode β Anode terminal of the PIN diode (unbanded end) |
| Pin 2 | Cathode β Cathode terminal of the PIN diode (identified by the polarity band on the package body) |
Typical Applications
BAP51-03,115 is suitable for 6 applications: RF Attenuators, RF Switching Circuits, Antenna Switching and Diversity, AGC and Transmit-Receive Power Control, General RF Signal Conditioning, Automotive RF Modules.
RF Attenuators
The BAP51-03,115 is a natural fit for voltage-controlled RF attenuator circuits because its forward resistance of 5.5 ohm varies predictably with DC bias current, allowing smooth, electronically controlled attenuation. The low 0.55 pF off-state capacitance keeps the signal path clean at high frequencies, while the 50 V rating tolerates the peak RF voltages present in receiver front-ends. In a typical pi-attenuator topology, the PIN diode is biased through an RF choke and series resistor with bypass capacitors isolating the DC network. The PIN charge-storage mechanism keeps intermodulation distortion low as long as stored charge exceeds the RF cycle charge, making this part well suited to AGC loops in wireless receivers where continuous gain adjustment is required.
Recommended
RF Switching Circuits
In series or shunt RF switch configurations, the BAP51-03,115 provides high off-state isolation thanks to its maximum 0.55 pF capacitance, which presents roughly 290 ohm of reactance at 1 GHz in series paths. Under forward bias, the 5.5 ohm on-resistance yields low insertion loss, and the 50 V reverse voltage rating supports switching applications with moderate RF voltage swings. Bias the diode with a DC current through an RF choke and decouple with ceramic capacitors so RF does not leak into the control line. The SOD-323 package occupies minimal board area (1.7 x 1.25 mm body), enabling compact switching matrices in antennas, filters, and test equipment signal-routing paths.
Recommended
Antenna Switching and Diversity
The BAP51-03,115 serves as the switching element between multiple antennas or antenna paths in wireless systems, where its automotive AEC-Q101 qualification and -65 C to +150 C temperature range ensure reliability in vehicle-mounted and outdoor equipment. The low capacitance minimizes the off-path loading that would otherwise detune a nearby active antenna, and the 500 mW dissipation rating comfortably handles transmitted signal levels in low-power radio systems. In a typical single-pole double-throw arrangement, two PIN diodes are biased complementarily through chokes, selecting one antenna while isolating the other. Careful bias-current setting determines the trade-off between insertion loss and switching speed in the selected path.
Recommended
AGC and Transmit-Receive Power Control
Automatic gain control circuits benefit directly from the BAP51-03,115's current-controlled resistance: increasing forward current smoothly reduces the series resistance toward 5.5 ohm, giving a monotonic, low-distortion gain control element. The PIN structure's charge storage means the RF signal sees an averaged resistance rather than a rectifying junction, which suppresses harmonic and intermodulation products compared to ordinary junction diodes. With a 50 mA forward current limit and 500 mW dissipation, the device handles the control-signal power requirements of typical receiver AGC loops and low-power transmit-receive switches. The AEC-Q101 qualification extends this use to automotive telematics and radio systems requiring high-reliability components.
Recommended
General RF Signal Conditioning
Beyond switching and attenuation, the BAP51-03,115 is specified by NXP for general RF applications, including series signal-path elements, phase-shifter networks, and protection clamps in measurement equipment. The combination of low capacitance (0.55 pF) and modest forward resistance (5.5 ohm) means the diode introduces minimal perturbation when correctly biased, which is essential in instruments where signal integrity is measured directly. Designers should route the bias network away from sensitive RF nodes and verify that peak signal voltage plus any DC offset stays below the 50 V rating. The small SOD-323 footprint and gull-wing leads allow straightforward automated assembly on standard surface-mount production lines.
Recommended
Automotive RF Modules
The AEC-Q101 qualification and wide -65 C to +150 C operating range make the BAP51-03,115 suitable for automotive RF subsystems such as remote keyless entry receivers, tire pressure monitoring sensors, and vehicle antenna modules. In these environments, the 50 V reverse rating provides margin against load-dump-induced transients on RF front-end lines, and the SOD-323 package withstands automotive reflow profiles and vibration. The low 0.55 pF capacitance preserves the sensitivity of compact antennas operating at 315 MHz, 433 MHz, and higher frequencies. Engineers should note the part is at end of life per NXP, so last-time-buy planning or qualification of the same-footprint BAP64 series is recommended for long-life automotive platforms.
Recommended
Recommended Products Summary
Engineering reference data for BAP51-03,115 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BAP51-02,115 | BAP64-02,115 | BAP64-03,115 |
|---|---|---|---|---|
| Package | SOD-323 (SC-76), 2-pin | SOD-323 (SC-76) - same | SOD-323 (SC-76) - same | SOD-323 (SC-76) - same |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| AEC-Q101 Qualification | Qualified | Qualified | Qualified | Qualified |
Key Differentiators
- Very low off-state capacitance for RF isolation (vs BAP64-02,115)
- Automotive AEC-Q101 qualification (vs Generic consumer-grade SOD-323 PIN diodes)
- Low forward resistance for low insertion loss (vs BAP51-02,115)
Design Notes
Lay out the BAP51-03,115 as a series RF element with the shortest possible leads to adjacent transmission lines; at 1 GHz the 0.55 pF off-state capacitance already limits isolation, so added parasitic inductance from long traces further degrades performance. Place the RF choke and bias-decoupling capacitors adjacent to the diode pads, and connect the bias network to the diode side of the DC block capacitor so RF and DC paths remain separated. The SOD-323 footprint uses a 1.3 mm lead pitch on a 1.7 x 1.25 mm body, fitting standard two-pad land patterns.
Respect the 500 mW power dissipation and 50 mA forward current limits. Estimated: dissipation is roughly VF x IF in conduction, and at maximum 50 mA drive the bias resistor must drop the remainder of the supply voltage; e.g., a 5 V bias rail with approximately 1 V across the diode needs about 80 ohm of series resistance. Derate dissipation as ambient temperature approaches the 150 C maximum operating point. Because the PIN resistance varies with current, calibrate attenuation curves at the actual bias current used in production, not just the nominal 5.5 ohm point.
Two pitfalls recur with this part. First, polarity: the SOD-323 cathode is marked by a band, and reversed PIN diodes in a switch simply leave the RF path permanently isolated - verify the banded end against the footprint silkscreen. Second, lifecycle: NXP has placed the BAP51-03 at end of life, so designs released today face sourcing risk; qualify the same-footprint BAP64 family or a verified cross-brand equivalent and secure last-time-buy stock. Third-party datasheet mirrors exist, but always design from the official NXP PDF for authoritative limits.
Compliance Information
AEC-Q101 qualified per distributor listings (Arrow, datasheets.com). RoHS/REACH/lead-free status not stated in the provided web data and therefore marked unknown; confirm on the NXP product page before purchase.
